Choosing supplements.

If you are going to use supplements it makes a lot of sense to know why. Ask yourself the following questions:

  • How much will the supplements cost?Bear in mind that most changes in the body take 2-4 months to become evident, so you can expect to take the supplements for a reasonable period of time.
  • What benefit am I expecting to get? - If you can't clearly identify your benefit, then you are likely to be wasting your money.
  • What are the side effects of using these supplements?Many supplements have little research into their side effects.
  • Are these supplements from a reputable company?If the manufacturing practices and quality control are poor, you will not be getting what you think you are buying.
  • Can I believe the marketing behind the product?Marketing is aimed at boosting sales. You are better off working out what you need, and then searching for it by comparing different company's products.

So why should I take supplements?

  • If your diet is poor you will be deficient in a range of vitamins, minerals and other nutrients. The first question you should ask yourself is, can I improve my diet? If you can't, then  supplementation with a multi vitamin/mineral could be helpful.
  • If you are ill you may well be depleted in certain nutrients. Vitamin D is commonly deficient in those that have been ill, partly due to lack of time in the sun.
  • If you have a specific health parameter you want to improve you may find that some supplements are good at improving it. For instance male fertility can be improved in many men with use of carnitine and zinc, while female menstrual problems can often be improved using the herb agnus castus.
  • During and before pregnancy supplementation can lead to better outcomes. The best known example is supplementation with folic acid. This leads to less chance of the baby developing neural tube defects and potentially spina bifida. 
  • If you drink or smoke then you are likely to be deficient in a number of nutrients. For instance smoking reduces the amount of vitamin C and carotenoids in your body. Alcohol reduces the amount of B vitamins.

What amount should I have?

  • For adults aged 19-50
    Vitamin/MineralRDA in mgUpper Limit in mg
    A - retinol0.83.0

    B1 - thiamin

    B2 - riboflavin1.2none
    B3 - niacin1535
    B6 - pyridoxine1.4100
    B12 - cyanocobalamin0.0024none
    C - ascorbic acid80 2000
    D - cholecalciferol0.0050.1
    E - tocopherol151000
    K - phylloquinone 0.11none
    Folic acid0.41.0
    Biotin 0.03none
    Molybdenum 0.0452
    Phosphorus 7004000

Government set RDAs

The Government sets recommended daily amounts - RDAs, that tell you what they think you should consume. These RDAs cover the first two types of supplement we identified in last weeks article what-are-supplements. These are vitamins and minerals, collectively known as micronutrients. Please remember this as I'll refer to them as micronutrients from now on. Typical RDAs for the best known micronutrients are shown in the table to the left.

There is much debate about how much of particular micronutrients you should consume. What you should always bear in mind is that what you need will vary depending on a number of factors.

  • What sex you are. For most micronutrients, females will need slightly less than the RDA, and males slightly more. Thre are two notable exceptions to this, and they are folic acid and iron, which are needed in greater amounts (roughly 50% more) by females who are menstruating regularly.
  • Your age. As children grow, their micronutrient needs gradually rise until they are equivalent with the adult values. Again there are exceptions such as calcium, which teenagers need more of to support their growing bones.
    • Your size. Generally speaking the larger framed you are the more micronutrients that you will need. Notice I say larger framed, which is a measure of your height and build, not your weight. Being overweight won't alter your need for micronutrients very much, although if you are eating a diet that has led to a lot of weight gain, it's likely you are not getting enough of them.
    • Your activity level. The more you exercise the more your need for micronutrients. The type of exercise you do, will determine what you need more of. For instance some endurance athletes become low in iron stores. The harder and longer you train for the more you will need of most micronutrients. However as your calorific needs will also rise, you should get enough, through an increased food intake. However this does assume that you eat more of all the types of food. If you make up your calorie deficit by consuming sugar laden sports drinks and bars, you may well end up requiring a multi vitamin/mineral to make up the difference.
    • Your general level of health. Various health conditions deplete us of micronutrients, increasing our needs. For instance those with multiple sclerosis or osteoporosis may benefit from vitamin D supplementation. Those with mental health problems, liver disease or heart disease may benefit from vitamin B supplementation.
If you consumed micronutrients based on the RDAs, and adjusted them according to the parameters above, the plain fact is that you will not be consuming enough. Generally speaking RDAs are set to prevent deficiency symptoms in 98% of the population. You don't need to be Einstein to work out that being just above the deficiency level is unlikely to lead to optimal health.

Optimal amounts below the upper limits.

In practice you need to consume more than the RDAs for optimal health. This is normally possible if you have a very healthy diet consuming a lot of the right foods. However, there are no hard and fast optimal amounts established for any micronutrients. My attitude is, that it is best to try and eat as healthy a diet as possible, and then supplement if you can identify a reason why a particular micronutrient would help you. If you do supplement, then you should exercise caution and be aware of the daily upper limits - ULs. These, like the RDAs, are set by Government bodies, and represent the maximum safe level for most people.

Many of the ULs can be legitimately questioned. For instance vitamin D was once considered dangerous to supplement, as it is fat soluble and can be stored in the body. However, there is good evidence that the body can handle large amounts of this vitamin. The upper limit is set at 0.1mg, however a day in the sun can quite naturally lead to the creation of 0.3mg of vitamin D leading us to ask ourselves is the UL really set at the correct level for most people? Sodium is another mineral, which has an UL that could be seen by many as too high. Many people in the medical profession would advise that an upper limit of 1000mg for sodium would be better for health than the current value of 2300mg. It could be argued that the vested interests of food manufacturers have influenced the setting of this particular upper limit. This is perhaps not surprising considering how much salt is used to entice consumers to consume more of many common products such as bread and breakfast cereals.

Some micronutrients have no published upper limit. This does not mean that they are safe to have in any quantity however. It is more a case that the committees that set the limits can't agree on what is a sensible level at which to set them. It is therefore best to consult a nutritional expert before embarking on the use of single vitamins or minerals, whether or not they have an upper limit set. It is worth remembering that people who don't store a particular micronutrient very well, may be able to supplement above the upper limiit quite safely.

Medications can interact with a number of micronutrients. For instance, vitamin E and the anticoagulant medication called warfarin, would not be a good combination. It would lead to excessively thin blood, and a danger of bleeding to death. Although vitamin E has a high upper limit (1000mg), in this instance it would be unsafe to supplement in any quantity without expert supervision. In fact, it is a good idea to get nutritional advice every time you consider changing your supplement regime, as the RDAs and ULs may not apply to you, and may also be in need of revision due to more scientific evidence that the Government committees have not yet considered.

Two other upper limits that many would take issue with are the ones for vitamin C and vitamin E. Vitamin C has many proponenets who like to supplement at well above the UL for a short period of time. For most this causes no complications other than possible gastric irritability. Vitamin E is less popular now than it was after some adverse findings with larger amounts. Many would prefer to see the upper limit reduced.

Finding out if you are deficient in a micronutrient.

If you already have a good diet and suspect that you are not in full health due to a micronutrient deficiency, then there are a number of ways of finding out if you are. Most micronutrients are detectable in the blood and test prices vary depending on which laboratories are used and whether you test for a single or multiple micronutrients. Other forms of testing may be cheaper. For instance zinc status can be assessed via a zinc taste challenge using zinc and distilled water. Many minerals can also be measured via analysis of the hair. These other forms of testing are normally cheaper than blood tests. Sometimes they are more accurate, but quite often less accurate than the blood tests. This really does depend on the specific mineral involved. 

To give you an idea of typical prices you may pay to find out if you need more of a given micronutrient the following are from testing labs that I deal with:

  • A test that looks at a range of vitamins and minerals £200-250.
  • A hair mineral analysis  £68
  • A test for one mineral or vitamin can range from £15 for magnesium to £40 or £72 for vitamin D depending on the lab.
  • Zinc taste challenge £5 at my practice.

Getting tested on the NHS in the UK is also a possibility. Most women would be able to get their iron levels tested this way. However you may not always get the test you want with the NHS. For example, with iron you will often get your iron levels in the blood via haematocrit and haemoglobin counts, but are unlikely to get your ferritin stores measured. Ferritin stores give a better idea of long term iron status than the blood levels.